The present program is directed toward the study of familial aggregation of blood pressure in children, from birth to adolescence. The extent of familial aggregation will be sought in different populations on the basis of different racial, socioeconomic, and environmental circumstances. The age at which sib-sib and parent-child aggregation of blood pressure first appears will be sought and evidence will be sought also for environmental variables that may influence the time of appearance of this aggregation: dietary, socioeconomic, and psychological variables will be investigated by epidemiological means. The stability of blood pressure tracking will be investigated in several population groups to determine if the present indications are accurate, that there is an established tendency toward blood pressure track that is detectable in early childhood. Preliminary evidence suggests, however, that the correlation successive blood pressure readings over a period of years rises with age, suggesting increasing stability of blood pressure track with aging, up to a stable level at approximately age 20. The present proposal will seek to determine how early in life evidence of tracking appears, and evidence of aggregation of blood pressure appears, in populations of infants and school children in Boston, providence, Rhode Island, and Barbados. These populations afford contrasting racial, socioeconomic, and cultural patterns, and will permit a determination of whether aggregation effects are subject to variation based on apparent environmental variables. Correlations with urinary kallikrein, plasma renin, and aldosterone, and catecholamines will be sought. Rates of frank hypertension in adolescent populations will also be sought in several communities and effectiveness of therapy in lowering these pressures will be investigated. The hypothesis will be explored that hypertension is a disease that starts in earliest childhood and that the blood pressure rank of a child, once established, will tend to be retained through-out life unless appropriate intervention has taken place.